The present invention relates to novel cancer markers and compositions and methods for cancer therapies. For example, the present invention provides for the detection of gene expression of particular marker genes as indicative of cancers, while control of said gene expression provides for intervention in cancer therapies and, in particular, glioma therapies.
The diagnosis of a brain or spinal cord tumor often comes as a shock, leaving confusion, uncertainty, fear, or even anger in its wake. Brain and spinal cord tumors are abnormal growths of tissue found inside the skull or the bony spinal column. The word tumor is used to describe both abnormal growths that are new (neoplasms) and those present at birth (congenital tumors). No matter where they are located in the body, tumors are usually classed as benign (or non-cancerous) if the cells that make up the growth are similar to other normal cells, grow relatively slowly, and are confined to one location. Tumors are called malignant (or cancerous) when the cells are very different from normal cells, grow relatively quickly, and can spread easily to other locations.
In most parts of the body, benign tumors are not particularly harmful. This is not necessarily true in the brain and spinal cord, which are the primary components of the central nervous system (CNS). Because the CNS is housed within rigid, bony quarters (i.e., the skull and spinal column), any abnormal growth can place pressure on sensitive tissues and impair function. Also, any tumor located near vital brain structures or sensitive spinal cord nerves can seriously threaten health. A benign tumor growing next to an important blood vessel in the brain does not have to grow very large before it can block blood flow. Additionally, if a benign tumor is found deep inside the brain, surgery to remove it may be very risky because of the chances of damaging vital brain centers.
When newly formed tumors begin within the brain or spinal cord, they are called primary tumors. Primary CNS tumors rarely grow from neurons (i.e., nerve cells that perform the nervous system""s important functions) because once neurons are mature they no longer divide and multiply. Instead, most tumors are caused by out-of-control growth among cells that surround and support neurons. Primary CNS tumors, such as gliomas and meningiomas, are named by the types of cells they contain, their location, or both.
In a small number of individuals, primary tumors may result from specific genetic diseases, such as neurofibromatosis and tuberous sclerosis, or exposure to radiation or cancer-causing chemicals. Although smoking, alcohol consumption, and certain dietary habits are associated with some types of cancers, they have not been linked to primary brain and spinal cord tumors. In fact, the cause of most primary brain and spinal cord tumors remains a mystery. Brain and spinal cord tumors are largely not preventable at this time and many tumors are associated with poor prognoses. For example, for brain stem gliomas the overall median survival time of patients in studies has been 44 to 74 weeks.
Studies suggest that new brain tumors arise in more than 40,000 Americans each year. About half of these tumors are primary, and the remainder are metastatic. Individuals of any age can develop a brain tumor. In fact, they are the second most common cause of cancer-related death in people up to the age of 35, with a slight peak in occurrence among children between the ages of 6 and 9. However, brain tumors are most common among middle-aged and older adults. People in their 60s face the highest risk. Each year 1 of every 5,000 people in this age group develops a brain tumor. Spinal cord tumors are less common than brain tumors with about 10,000 Americans developing primary or metastatic spinal cord tumors each year. Although spinal cord tumors affect people of all ages, they are most common in young and middle-aged adults.
A) Detection
Brain and spinal cord tumors cause many diverse symptoms, which can make detection tricky. Whatever specific symptoms a patient has, the symptoms generally develop slowly and worsen over time. The brain orchestrates behavior, movement, feeling, and sensation. It controls automatic functions like breathing and heartbeat. Many of these important functions are controlled by specialized brain areas. For example, the brain""s left and right hemispheres jointly control hearing and vision; the front part of each hemisphere controls voluntary movements, like writing, for the opposite side of the body; and the brain stem is responsible for basic life-sustaining functions, including blood pressure, heartbeat, and breathing. As a result, brain tumors can cause a bewildering array of symptoms depending on their size, type, and location. Certain symptoms are quite specific because they result from damage to particular brain areas. Other, more general symptoms are triggered by increased pressure within the skull as the growing tumor encroaches on the brain""s limited space or blocks the flow of cerebrospinal fluid (fluid that bathes the brain and spinal cord). Some of the more common symptoms of a brain tumor include headaches, seizures, nausea, vomiting, vision and hearing problems, behavioral and cognitive symptoms, motor problems, and balance problems. Common symptoms that result from spinal chord tumors include: pain, sensory changes, and motor problems.
Once a physician suspects a brain or spinal cord tumor because of a patient""s medical history and symptoms, a variety of further tests are available for diagnosing the tumor. The first test is often a traditional neurological exam. A neurological exam checks eye movement, eye reflexes, and pupil reaction, reflexes, hearing sensation, movement, balance, and coordination. The next step in diagnosing brain tumors often involves X-rays or special imaging techniques and laboratory tests that can detect the presence of a tumor and provide clues about its location and type. Special imaging techniques, especially computed tomography (CT) and magnetic resonance imaging (MRI), have dramatically improved the diagnosis of CNS tumors in recent years. In many cases, these scans can detect the presence of a tumor even if it is less than half-an-inch across. However, the equipment is expensive and complex and such imaging techniques can miss tumors (e.g., small tumors), particularly at early stages where treatment is more likely to succeed. Such equipment also does not provide information relating to the morphological identity of the tumor. A third imaging technique called positron emission tomography (PET) provides a picture of brain activity rather than structure by measuring levels of injected glucose that has been labelled with a radioactive tracer. Glucose is used by the brain for energy. Detectors placed around the head can spot the labelled glucose, and a computer uses the pattern of glucose distribution to form an image of the brain. Since malignant tissue uses more glucose than normal tissue, it shows up on the scan as brighter or lighter than surrounding tissue. Currently, PET is not widely used in tumor diagnosis, in part because the technique requires very elaborate, expensive equipment, including a cyclotron to create the radioactive glucose.
Laboratory tests commonly used include the electroencephalogram (or EEG) and lumbar puncture, also known as the spinal tap. The EEG uses special patches placed on the scalp or fine needles placed in the brain to record electrical currents inside the brain. This recording can help the physician see telltale patterns in the brain""s electrical activity that suggest a brain tumor. Repeated EEG recordings can be particularly helpful in determining whether an abnormality in brain activity is getting worse. In lumbar puncture, doctors obtain a small sample of cerebrospinal fluid. This fluid can be examined for abnormal cells or unusual levels of various compounds that suggest a brain or spinal cord tumor. However, these techniques are limited in their ability to decisively identify and characterize tumors. In view of the limitations of current cancer detection technologies, what is needed are tumor-specific markers that can be used to detect early stage cancer (e.g., cancers too small to be detected by conventional techniques) and can provide information about the morphology of the cancer.
B) Treatment
To date, treatment of tumors requires intense therapies with dramatic and sometimes fatal side effects. The three most commonly used treatments are surgery, radiation, and chemotherapy. Surgery to remove as much tumor as possible is usually the first step in treating an accessible tumorxe2x80x94that is, a tumor that can be removed without unacceptable risk of neurological damage. Although research has led to advances in neurosurgery that make it possible for doctors to reach many tumors that were previously considered inaccessible, not all tumor can be treated with surgery. If the tumor is malignant, doctors often recommend additional treatment following surgery, including radiation and/or chemotherapy.
In radiation therapy, the tumor is bombarded with beams of energy that kill tumor cells. Traditional radiation therapy delivers radiation from outside the patient""s body, is usually begun a week or two after surgery, and continues for about six weeks. The dosage is fairly uniform throughout the treated areas, making it especially useful for tumors that are large or have infiltrated into surrounding tissue. However, when traditional radiation therapy is given to the brain, it may also cause damage to healthy tissue.
Chemotherapy uses tumor-killing drugs that are given orally or injected into the bloodstream. Because not all tumors are vulnerable to the same anticancer drugs, physicians often use a combination of drugs for chemotherapy. Chemotherapeutic drugs generally kill cells that are actively growing or dividing, making these compounds relatively more effective against malignant tissue, which contains a high proportion of growing and dividing cells, than to most normal cells. Because a high proportion of the cells in the skin, gastrointestinal tract, and other areas are also growing and dividing at any given time, the side effects commonly observed include skin reactions, hair loss, and digestive disturbances. The drugs most commonly used for CNS tumors are known by the initials BCNU (sometimes called carmustine) and CCNU (or lomustine). Each of these techniques poses significant health risks to treated individuals and does not guarantee elimination of the tumor. Surgery and radiotherapy alone are seldom curative; with the best of care, median survival is under one year for many cancers. Moreover, despite major efforts to introduce new adjunctive therapies, the prognosis for patients with malignant gliomas has remained essentially unchanged for the past thirty years. Thus, the art is in need of new therapies that avoid the dangerous and undesired side-effects of current technologies, while allowing effective tumor reduction or elimination.
The present invention relates to novel cancer markers and compositions and methods for cancer therapies. For example, the present invention provides for the detection of gene expression of particular marker genes as indicative of cancers, while control of said gene expression provides for intervention in cancer therapies and, in particular, glioma therapies.
For example, the present invention provides methods for detecting cancer in a subject suspected of having cancer comprising detecting the presence of TAX-1 in a sample from the subject. In some embodiments of the present invention, the sample comprises cerebrospinal fluid, although any suitable sample may be used. In some embodiments, the subject comprises a human subject. In certain embodiments, the cancer comprises a cancer of the central nervous system. For example, in some embodiments, the cancer of the central nervous system comprises a glioma. In some embodiments of the present invention the detecting of the presence of TAX-1 comprises detecting TAX-1 protein by any suitable means. In some embodiments, TAX-1 protein is detected by exposing TAX-1 protein (e.g., from a cell extract) to a TAX-1-specific antibody and detecting the presence of the antibody (e.g., detecting the presence of an antibody/TAX-1 complex). In other embodiments of the present invention the detection of the presence of TAX-I comprises detecting TAX-1 mRNA by any suitable means. In some embodiments, detecting TAX-1 mRNA comprises exposing TAX-1 mRNA to a nucleic acid probe complementary to TAX-1 mRNA. In some embodiments of the present invention, the detection of the presence of TAX-1 comprises measuring the amount of TAX-1 protein or mRNA in the sample. In certain embodiments, the amount of TAX-1 protein or mRNA is compared to the amount of TAX-1 protein or mRNA from a control sample (e.g., a sample of a subject without cancer and/or a sample of a subject known to have cancer).
The present invention also provides a methods for regulating cell migration by reducing TAX-1 expression, comprising providing: a cell expressing TAX-1 and an agent capable of reducing TAX-1 expression; and exposing the cell to the agent under conditions wherein the agent reduces TAX-1 expression. Any agent that reduces TAX-1 expression finds use with the present invention. In some embodiments, the agent comprises an antisense compound. In certain embodiments, the antisense compound comprises an antisense oligonucleotide. In specific preferred embodiments, the antisense compound comprises SEQ ID NO:1. In other embodiments of the present invention, the agent comprises an antibody. In preferred embodiments, the antibody comprises at least one monoclonal antibody. In some embodiments of the present invention, the exposing of the cell to the agent comprises administering the agent to a subject comprising the cell (e.g., a host, wherein the cell is part of a tissue of the host).
The present invention further provides methods for regulating TAX-1 expression in a subject suspected of having cancer, comprising providing: a subject suspected of having cancer and an agent capable of reducing TAX-1 expression; and administering the agent to the subject under conditions wherein the agent reduces TAX-1 expression. In some embodiments, the method further comprising the step of detecting the expression of TAX-1 in a sample (e.g., a tissue or fluid sample) from the subject. Detection may be made for any number of reasons including, but not limited to, testing the ability of the agent to alter TAX-1 expression. In some embodiments, the agent comprises an antisense compound (e.g., an antisense oligonucleotide including, but not limited to, SEQ ID NO:1). In other embodiments, the agent is an antibody (e.g., one or more polyclonal or monoclonal antibodies).
The present invention also provides methods for testing the ability of a compound to alter TAX-1 expression comprising providing: a cell capable of expressing TAX-1, and a test compound; exposing the cell to the test compound; and detecting the ability of the compound to alter the expression of TAX-1 in the cell. In some embodiments of the present invention, the cell is treated in vitro. In other embodiments, the cell is treated in vivo. In some embodiments, the test compound comprises an antisense compound. In other embodiments, the test compound comprises at least one drug. In preferred embodiment, exposing the test compound to the cell comprises administering the agent to a subject comprising the cell (e.g., a host, wherein the cell is part of a tissue of the host). In other preferred embodiments, the detection of the ability of the test compound to alter expression of TAX-1 comprises detecting a change in cell migration (e.g., using a cell migration assay). In other preferred embodiments, the detection of the ability of the test compound to alter expression of TAX-1 comprises detecting TAX-1 expression.